netdev - Re: [PATCH v16 05/22] cxl: Add function for type2 cxl regs setup

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Message-ID: <682e1b368fc8_1626e100c3@dwillia2-xfh.jf.intel.com.notmuch>
Date: Wed, 21 May 2025 11:28:06 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: <alejandro.lucero-palau@....com>, <linux-cxl@...r.kernel.org>,
	<netdev@...r.kernel.org>, <dan.j.williams@...el.com>, <edward.cree@....com>,
	<davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<edumazet@...gle.com>, <dave.jiang@...el.com>
CC: Alejandro Lucero <alucerop@....com>, Ben Cheatham
	<benjamin.cheatham@....com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v16 05/22] cxl: Add function for type2 cxl regs setup

alejandro.lucero-palau@ wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> Create a new function for a type2 device initialising
> cxl_dev_state struct regarding cxl regs setup and mapping.
> 
> Export the capabilities found for checking them against the
> expected ones by the driver.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> Reviewed-by: Ben Cheatham <benjamin.cheatham@....com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
>  drivers/cxl/core/pci.c | 62 ++++++++++++++++++++++++++++++++++++++++++
>  include/cxl/cxl.h      |  3 ++
>  2 files changed, 65 insertions(+)
> 
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index e2b6420592de..b05c6e64bfe2 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -1095,6 +1095,68 @@ int cxl_pci_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
>  }
>  EXPORT_SYMBOL_NS_GPL(cxl_pci_setup_regs, "CXL");
>  
> +static int cxl_pci_accel_setup_memdev_regs(struct pci_dev *pdev,
> +					   struct cxl_dev_state *cxlds,
> +					   unsigned long *caps)
> +{
> +	struct cxl_register_map map;
> +	int rc;
> +
> +	rc = cxl_pci_setup_regs(pdev, CXL_REGLOC_RBI_MEMDEV, &map, caps);
> +	/*
> +	 * This call can return -ENODEV if regs not found. This is not an error
> +	 * for Type2 since these regs are not mandatory. If they do exist then
> +	 * mapping them should not fail. If they should exist, it is with driver
> +	 * calling cxl_pci_check_caps() where the problem should be found.
> +	 */

The driver should know in advance if calling:

    cxl_pci_setup_regs(pdev, CXL_REGLOC_RBI_MEMDEV, &map);

...will fail. Put that logic where it belongs in the probe function of
the type-2 driver directly. This helper is not helping, it is just
obfuscating.